Process for exchanging cations from aqueous solutions



Patented June 12,1945 I PROCESS FOR EXCHANGING CATIONS FROM AQUEOUS SOLUTIONS Otto Liebknecht, Neubabelsberg, near Berlin, Germany, assignor to The Permutit Company, New York, N. Y., a corporation of Delaware No Drawing. Application April 5,1938, Serial No. 200,243. In Germany April 20, 1937 4 Claims.

This invention or discovery relates to the manufacture of carbonaceous zeolites; and it comprises an improvement in the manufacture of ion exchanging carbon materials, or carbonaceous zeolites, by the action of sulfuric acid on carbonaceous materials with limitation of the amount of actual carbon formed in the action wherein the sulfuric acid used already contains dissolved carbon compounds, the material treated advantageously also containing sulfur oxides in organic combination, as with dried sulfite waste liquor; all as more fully hereinafter set forth and as claimed. I

In a prior and copending application Serial No. 10,127, filed March 6, 1935, wherewith the present application contains certain matter in common, I have described and claimed active ion exchanging bodies made by the treatment of various materials, notably lignite, bituminous coal and similar materials, with strong sulfuric acids or a sulfonating body such as chlor-sulionic acid and S03 gas. The actions are to a large extent unknown but they involve sulfonation or sulfation; S03 going into organic combination. One undesirable action is charring with productionof carbon assuch. This, to a certain extent, is inevitable but it is not desirable. The products of the sulfating action, after washing free of solubles, are highly insoluble and of an acidic nature and can be used in purifying water in a way analogous to that with ordinary silicate zeolites, glauconite, etc., being alternately contacted with flowing water and regenerated with a salt solution. They have, however, a considerably greater capacity, both per unit volume and unit weight. They have'the further great advantage over silicate zeolites in that they can be regenerated an indefinite number of times with acids without injury. This makes practicable their use in removing cations from water and substituting hydrogen therefor in the water. Hard Water containing calcium and magnesium salts can have the cations removed with carbonaceous zeolites leaving the corresponding acid in solution. Where the acid is carbonic acid, it can afterwards be removed by aeration.

\ The actions of sulfuric acid and of SO: gas in treating lignite, soft coal and other materials are complex and somewhat diflicult to control In particular, insofar as the charring action is exerted, there is a production of elemental car- 'bon which is of no great value for the purposes of these preparations. Charring is due in part to the withdrawal of water from carbohydrates. This charring difficulty is one of the reasons for preferring the use of lignite and sort coal to. ordinary vegetable materials such as wood ch1ps,-

etc. The action is less violent with lignite and coal.

In making good ion exchange material, a strength of acid of at least '70 per cent is advantageous and S03 is often desirable, since the reaction can be easily controlled. In the latter event the S03 is used as a vapor, advantageously diluted somewhat with inert gases.

I have now discovered that by the use of sulfuric'acid, already mixed or combined with carbon compounds, lbetter iOn exchanging bodies are produced. The carbon compounds associated with the acid no doubt contribute to the,product.

The action is considerably less violent and higher heats are easily avoided. There is much less charring with production of elemental carbon as an inert constituent if heating is properly controlled.

Acidic substances of the character I desire may be made by treating sulfuric acid with a petr0- leum oil until the first energetic reaction is over. A sludge forms and settles to the bottom. Excess oil, if any, in the sludge may then be removed or allowed to remain. However, waste acids of a character suitable for my purposes are available in many industries and particularly in petroleum refining. Most petroleum products are treated with sulfuric acid at one stage or another and there is an accumulation of separated acid sludge. The acid used is ordinarily of a strength not less than 66 B.- (93-97 per cent H2804) and it is often fuming acid; that is, H2804 containing S03 in large amount.- The sludge is generally of fluent character, sometimes being quite liquid, and contains free and combined sulfuric acid, asphaltic matter, neutral oil and miscellaneous compounds. Such 'an acid sludge is, according to one embodiment or the invention, caused to act upon a suitable carbonaceous material, at a suitable elevated temperature. Among suitable carbonaceous materials are bituminouscoal, anthracite, semi-coke, pitch, lignite, peat, charcoal, cork, wood, straw, sugar, dextrine, and other carbonizable substances, or substances. containing carbonizable constituents, exemplified by soaps, concentrated or thickened sulfite waste liquor, fats and fatty generally called "ligno-sulfonic acids, although I they are not formed with the aid of sulfuric acid.

tures of about 90 to 250 C., the temperaturebeing controlled so as to yield insoluble products of the character desired, but to avoid any extensive carbonization or coking of the reaction mixture.

In some cases higher concentrations of acid are desirable than those obtained from acid sludge. In such cases, additional quantities of concentrated acid are added to the sludge or the reaction mixture. The added acid can be concentrated sulfuric acid, or other acids such as chlorsulfonic acid and fuming sulfuric acid, or acid anhydrides such as sulfuric anhydride or phosphoric anhydride. Using sulfuric anhydride, 1. e. S: (sulfur trioxide), this is best employed as a vapor, and in conjunction with inert diluent gases.

As a rule, the process works best when the acid concentration of the sludge or the sludge and acid mixture, is at least 70 per cent H2804.

It has been discovered by another that in the production of ion-exchange substances from coal,

etc., with the acid of sulfuric acid, better products are obtained when an oxidation promoting agent is present. This expedient is also useful in the present invention. Products of 20 to 40 per cent better exchange capacity are obtained when there is added to the reagents, either before or during the heat treatment, a suitable quantity of an oxidation promoting agent, for example nitric acid of -86 per cent strength (at which concentra tion it can be mixed with concentrated sulfuric acid without development of heat), chromic acid, permanganates and persulfates, and certain anhydrous salts of chromium, aluminum, manganese, cobalt, nickel and iron. These materials can be added at any stage'in the process, but their effect is greatest when they are present during the heat treatment.

In the oil refining 'art, the acid sludge obtained as described is usuallyprocessed for recovery of sulfuric acid therefrom. This involves diluting the sludge with water, whereupon oil and lighter tarry matters, etc., are separated as a layer overlying a layer of impure dilute sulfuric acid. The decanted sulfuric acid (sludge acid) is then usually concentrated by evaporation, and the product is a fairlyl concentrated but impure product known as black acid.

These impure sulfuric acids separated from acid sludge contain substantial quantit es of soluble organic compounds, and are useful in my process. Concentrated to 70 per cent or higher H2804, they can be used to treat coal or other carbonaceous substances, to secure better products than are obtainable with pure sulfuric acid. The acid obtained by dilution of ac d sludge may be used with advantage in the processes of my copending application Serial No. 10,127 where sulfuric acid is indicated. A better product is obtained using this type of acid which is, so to speak, buffered against violent action by the contained carbon compound.

With proper control of conditions. the reaction products are usually of excellent physicalcharacter, being readily prepared as uniform granules of the right degree of porosity and size and having good resistance to wear and abrasion. However, it is sometimes advantageous to in- The ranules can be added before, during or after the heat treatment, depending on the character of the reacting substances.

In a modification of the invention, excellent ion exchange bodies are made by treatment of acid sludge alone; the sludge supplying both the carbonaceous component and the acidic component. If heating of an acid sludge be conducted at a temperature of to C., after or before concentratiomSOz is given off. Evolution is more active at higher temperatures. By continuing the heating until a sample on admixture with water no longer gives up color and there is no separation of oil, an active ion exchanging body is produced. This may be granulated, washed and used for treating water, either as a sodium zeolite or as a hydrogen zeolite. While higher and lower temperatures of reaction may be used, in a general way temperatures between 90 and 100 C. are best. However, good products may be obtained by heating up to 250 C. Higher temperatures resulting in extensiv cokin are not desirable.

Following are three specific examples of processes within the purview of the invention, directed'to making cation-exchanging substances from acid sludge alone.

Example 1.An acid sludge derived from a petroleum works is slowly heated while being stirred. At about 85 C. a plainly perceptible odor of S02 arises. The temperature is then slowly increased and the S02 development becomes more active. Any sudden foaming of the mass is prevented by stirring. When the temperature is increased to about 160, 2. point is reached where the development of sulphurous acid seems to decrease, whereupon one determines by mixing a sample with water whether the conversion process is complete. The mass'is now diluted with Water and the active substance, which looks something like coal, is separated from the sulfuric acid by filtration. The sulfuric acid can be concentrated and used again. The sulfur dioxide given off can also be made use of so that no appreciable loss in sulfuric acid results.

If desired, the temperature can be kept at a lower point, for example at in which case the development of S02 and the conversion to the desired substances take more time. The temperature can likewise be maintained at a higher value, up to the limit set forth. correspondingly shorter periods of reaction result.

Example 2.--A batch of 500 parts by weight of acid sludge with a specific gravity of about 1.69 is heated slowly and stirred, until a temperature of about is reached. S02 development begins at about 80 during the heat treatment, and becomes more and more active as the temperature rises to about 100. The heat treatment is carried on for about 1.5 hours, during which period the temperature is kept at 160 C. for about a half hour. A sample'is now taken and is diluted with water. Should this sample still show that conversion is not complete, the heat treatment is con- ,.tinued for some time longer. In general, however,

the above stated time suffices for completion. Now the whole mass is cooled and immersed in water and the sulfuric acid is separated from the coallike active substance present in the water. About 54 parts by weight (air dried) of this carbonaceous substance are obtained. The filtrate consisting of sulfuric acid can be reconverted into sulfuric acid of the desired strength by evaporative concentration, in connection with which the concentration ofthe sulfuric acid is increased as much as possible by systematic leaching.

Example 3.,-Petroleum refining sludge is diluted to produce a 70 per cent'acid and the oily separation removed. About 50 parts of granulated commercial soft coal or lignite with not more than 15 per cent Water are mixed into 200 parts of the acid. so obtained. Stirring cold, .during mixture, the temperature rises to 70-80 C. The.

, moved. The carbonaceous 'zeolite can then be regenerated. either with salt or with dilute acid, ay 3 per cent sulfuric acid. In the former case, on re-use of the zeolite with hard water, there is an ion exchange, sodium being exchanged for the calcium and magnesium of the hard water. The material is an excellent ion exchanger and has the merit of having greater capacity or longer life between regenerations. If regeneration is with dilute acid, then the zeolite extracts cations .such as calcium, magnesium and sodium, substi tuting hydrogen therefor. This leaves the eflluent from the exchanger of acid nature. Insofar as I acidity is due to CO2 it can be removed by aerae tion and in other well known ways. Insofar as acidity is due to mineral acids, sulfuric and hydrochloric, it can be neutralized by an addition of the proper amount of water softened by ion exchange and containing soda. Or, the free acids may be removed by the use of special carbonaceous zeolites adapted to extract anions from flowing Water.

While treatment times and temperatures vary with the materials treated, the simple test given is a good guide for ascertaining the optimum conditions. That is, when a sample of the reaction mixture is immersed in water, and gives up no coloring matter; etc., to the water, this is an indication that conversion is complete for the present purposes.

What I claim is: r

1. A process for effecting cation exchange in liquids which comprises contacting said liquids with a sulfated asphaltic material.

2. A process for reducing temporary hardness in liquids which comprises contacting said-liquids with a sulfated asphaltic material. I

3. A process for exchanging cations from aqueous solutions and effecting regeneration of the cation exchange medium, comprising first effecting exchange of cations with a sulfated asphaltic material, and thereafter regenerating said sulfated asphaltic material by treatment with a different cation containing liquid.

4. A process for recovering cations from aqueous solutions and effecting regeneration of the cation exchange medium, comprising first effecting exchange of cations with a sulfated asphaltic material, thereafter regenerating said sulfated asphaltic material by treatment with a difierent cation containing liquid, and recovering the originally exchanged cations from the ellluent of the regeneration treatment.

o'r'ro LIEBKNECHT. 

